Using GaN Crystal Non-polarity White LEDs to Exhibit

Seoul Semiconductor developed a combination of fluorescent materials on a 1mm square blue LED chip, achieving a white LED with a luminous flux of about 500lm, and at the "Japan's 5th New Generation Lighting Technology Exhibition" (January 2013 From April 16 to 18 at Tokyo Ariake International Convention and Exhibition Center). The feature of this development product is that it is easier to increase the brightness than the previous product. At present, Mitsubishi Kagaku Media has decided to adopt this development product for its LED bulb product (brand name “Verbatim”), and it is scheduled to start mass production in March 2013.

The light output power can be easily increased because of the use of "non-polar faces" of GaN crystals and suppresses crystal defects. The blue LED chip used in this development is a GaN-based semiconductor crystal grown on the non-polar surface of a GaN substrate manufactured by Mitsubishi Chemical.

An ordinary blue LED chip is formed by growing a GaN-based semiconductor on a sapphire substrate. In this case, the c-plane (polar plane) of the GaN crystal is used.

The non-polar surface is a surface perpendicular to the polar surface. When a polar plane is used as a growth surface, a piezoelectric field is generated, and electrons and holes injected into the light-emitting layer are separated from each other, which reduces the probability of recombination that promotes light emission. The non-polar surface as the growth surface is not easily affected by the piezoelectric field, so the luminous efficiency can be easily improved.

The crystal defect of this development product is only 1×104cm-2 at the least. The common blue LED chip has a large difference in the lattice constants of the GaN-based semiconductors on the sapphire substrate and the sapphire substrate, so the crystal defect density reaches 5×10 8 cm −2 .

With the above means, the development of the product even at high current density, the light output power is not easy to reduce, thereby increasing the light output power of a single white LED. The goal in the future is to achieve a luminous flux of 1,000 lm by combining a 1 mm square blue LED chip with a phosphor.

Seoul Semiconductor also said in the booth that the company is developing UV LED chips that use non-polar surfaces of GaN crystals. Combining an ultraviolet LED chip with red, green, and blue fluorescent materials, a backlight for a liquid crystal panel with high color rendering and a wide range of color expression can be easily realized. However, UV LEDs currently have lower luminous efficiency than blue LEDs. Therefore, the company intends to use non-polar surfaces to achieve high luminous efficiency UV LED.